| Abstract | dc.description.abstract | On 27 February 2010 the Mw 8.8 Maule earthquake in Central Chile ruptured a seismic gap where significant
strain had accumulated since 1835. Shortly after the mainshock a dense network of temporary seismic stations
was installed along the whole rupture zone in order to capture the aftershock activity. Here, we present
the aftershock distribution and first motion polarity focal mechanisms based on automatic detection algorithms
and picking engines. By processing the seismic data between 15 March and 30 September 2010
from stations from IRIS, IPGP, GFZ and University of Liverpool we determined 20,205 hypocentres with magnitudes
Mw between 1 and 5.5. Seismic activity occurs in six groups: 1.) Normal faulting outer rise events 2.)
A shallow group of plate interface seismicity apparent at 25–35 km depth and 50–120 km distance to the
trench with some variations between profiles. Along strike, the aftershocks occur largely within the zone
of coseismic slip but extend ~50 km further north, and with predominantly shallowly dipping thrust mechanisms.
Along dip, the events are either within the zone of coseismic slip, or downdip from it, depending on
the coseismic slip model used. 3.) A third band of seismicity is observed further downdip at 40–50 km depth
and further inland at 150–160 km trench perpendicular distance, with mostly shallow dipping (~28°) thrust
focal mechanisms indicating rupture of the plate interface significantly downdip of the coseismic rupture,
and presumably above the intersection of the continental Moho with the plate interface. 4.) A deep group
of intermediate depth events between 80 and 120 km depth is present north of 36°S. Within the Maule segment,
a large portion of events during the inter-seismic phase originated from this depth range. 5.) The
magmatic arc exhibits a small amount of crustal seismicity but does not appear to show significantly enhanced
activity after the Mw 8.8 Maule 2010 earthquake. 6.) Pronounced crustal aftershock activity with
mainly normal faulting mechanisms is found in the region of Pichilemu (~34.5°S). These crustal events
occur in a ~30 km wide region with sharp inclined boundaries and oriented oblique to the trench. The
best-located events describe a plane dipping to the southwest, consistent with one of the focal planes of
the large normal-faulting aftershock (Mw=6.9) on 11 March 2010. | es_CL |
